Background: The incidence of breast cancer after reduction mammoplasty has been demonstrated to be lower than the general population in several large registry trials performed in primarily European populations; North American data is lacking. Tissue rearrangement during reduction mammoplasty may lead to abnormal breast imaging results postoperatively resulting in more challenging screening.The purpose of this study was to describe the incidence and treatment of breast cancer after reduction mammoplasty in a more contemporary Canadian population, and to better understand the use of breast cancer screening modalities in these patients. Methods: This population-based retrospective analysis utilized the Discharge Abstract Database held by the Canadian Institute for Health Information (CIHI) and the National Ambulatory Care Reporting System (NACRS) to identify all women 20 or older who underwent reduction mammoplasty in Alberta, Canada between 2003 and 2007. The incidence and treatment of breast cancer was compared among patients who underwent reduction mammoplasty and age-sex matched controls in Alberta. Imaging utilization post mammoplasty, including use of mammography, ultrasound and breast biopsy was also compared between these two groups. Results: A total of 8,021 patients over 20 years old underwent reduction mammoplasty during the study period. Patients were followed for an average of 12.6 years. Most women (6,417, 80%) underwent reduction mammoplasty surgery between the ages of 20-50. Compared to controls, women who underwent reduction mammoplasty had more comorbidities (Charlson Comorbidities > 1: 5.2% vs 4.2% controls, p < 0.0001). Overall, 89 (1.1%) patients who underwent reduction mammoplasty developed breast cancer after surgery, compared to 453 (1.9%) controls (p < 0.0001). Among patients diagnosed with breast cancer, there was no difference in patient characteristics, tumor size, histology and grade between the two groups. Fewer patients presented with metastatic disease after reduction mammoplasty (0% vs 5.1%, p = 0.043). The surgical treatment differed between groups; patients who underwent reduction mammoplasty were significantly more likely to undergo mastectomy for breast cancer (41.6% vs 1.5%, p < 0.0001). Women who underwent reduction were more likely to undergo mammography (66.7% vs 58.7%, p < 0.001), ultrasound (29.2% vs 26.2%, p < 0.0001) and biopsy for benign disease (7.2% vs 6%, p = 0.0001) compared to controls. Conclusions: Despite an increased frequency of breast cancer screening, the incidence of breast cancer is lower after reduction mammoplasty compared to women who did not undergo breast reduction. After a diagnosis of breast cancer, surgical treatment patterns differ between groups despite similarities in tumor characteristics, whereby mastectomy is more common in those who have undergone breast reduction.